A thin plastic liner or the like is often employed in a shipping box or other container to increase the shelf-life of foods or other perishable commodities or to prevent leakage or spillage of product from a sealed shipping container. Such plastic liners are often in bag form.
A common method of lining containers has been to manually place the liner over the open end of the container and then drawing the liner into the container using a vacuum as shown in U.S. Pat. No. 4,052,931 to Morse et al., or by blowing the liner into the container as shown in U.S. Pat. No. 4,537,584 to Everman et al. Attempts have also been made to automatically open the liner before placing the liner over the open end of the container by using a vacuum assembly as shown in U.S. Pat. No. 4,522,012 to Nelson, U.S. Pat. No. 4,083,293 to Goldstein, and U.S. Pat. No. 4,537,584 to Everman et al. However, the use of such vacuum assemblies in a totally automated lining process has been problematic. Vacuum cup or vacuum bar assemblies in totally automatic assemblies do not provide a positive grasp on each side of the liner to enable the sides of the liner to be completely pulled apart. In addition, simply separating the sides of the bag at the open end does not completely open the bag since the sides of the bag tend to cling together due to surface tension or other adhesion between the inner surfaces of the liner. If the liner is not completely opened before it is placed over the container, the liner can tear. Attempts to break such surface tension or adhesion while using vacuum cups or bars to separate the sides of the liner have been unsuccessful.
Another method is disclosed in U.S. Pat. No. 5,059,084 to Krein. There, two methods are discussed for installing a liner in a semi-tractor trailer. In the first method, an unopened liner is manually unrolled into the trailer with the open end facing the entrance of the trailer (no discussion is provided on how the liner will be unrolled or by what mechanism). A blower is secured to the open end and the liner inflated. When the liner is fully expanded, the open end can be sealed against the entrance using, for example, tension bars 28 and 30. In an alternative embodiment shown in FIG. 8 (see col. 5 line 8), the liner is unrolled and the open end is sealed against the entrance. A vacuum is drawn through a pair of vertical vacuum members 24 inserted at the rear of the trailer near the door hinges. These members evacuate the air in the trailer, drawing the liner up against the trailer wall. Krein suggests that other kinds of vacuum arrangements can be used, such as horizontal members extending from the door of the trailer back into the rear of the container. However, Krein does not disclose whether such members would be permanently installed in the trailer, or simply inserted during the procedure. If the latter, Krein does not suggest where the members would be located or how they would be inserted and withdrawn.
Yet another method is described in U.S. Pat. No. 4,874,354 to Johnson et al. There, a liner is positioned above a container with the liner opening facing toward the container. A jaw assembly grasps the liner and fits the unsealed end of the liner around the opening of the container; subsequently, the liner is inverted into the container using a vacuum created in the container using a plenum over which the container has been positioned. Once in the container, the liner expands in the inverted configuration to line the inside of the container. A drawback with this invention is that there must be sufficient room above the container to accommodate the jaw assembly and an extended liner while the liner is being cuffed to the container. This is apparent from FIG. 1 of the '354 patent wherein the liner is in an extended configuration as it is being cuffed to the container. If the liner is not extended, the vacuum plenum will not be able to efficiently draw the bag into the container. Furthermore, this invention will only work if the container is substantially open at the bottom for providing access of the plenum to the inside of the container. Still further, with this device, the liner is inverted in the container. This can cause a configuration problem if a specific side of the liner must contact the inner surface of the container. For example, if one side of the liner is more or less water permeable.
What is therefore needed is a quick and reliable method and apparatus for lining a container having one or two openings. Furthermore, the apparatus must also be compact so as to minimize its space requirements. Still further, the apparatus must allow for lining of a container without inverting the liner during the lining process.